Stereotactic body radiotherapy (SBRT) versus androgen deprivation therapy (ADT) for oligometastatic prostate cancer: protocol for a prospective randomised control clinical trial

Introduction: The systemic therapy, especially androgen deprivation therapy (ADT), is currently recommended for patients with oligometastatic prostate cancer (PCa). However, the results have not been satisfactory including adverse reactions and castration resistance. Therefore, it is necessary to explore more effective treatment to prolong biochemical progression-free survival (bPFS) and delay the start of hormonal therapy for treating oligometastatic PCa. Stereotactic body radiotherapy (SBRT) is an emerging treatment alternative for patients with oligometastases with high local control rates and minimal toxic effects. This prospective trial aims to demonstrate whether SBRT for the oligometastases of hormone-sensitive PCa can delay the start of ADT and prolong the time from inception of the study to castration-resistant prostate cancer (CRPC).

Methods and analysis: Patients with ≤3 oligometastatic recurrences, diagnosed on Ga-68 prostate-specific membrane antigen PET/CT, will be randomised in a 1:1 ratio between arm A (ADT only) and arm B (SBRT for oligometastases only). SBRT is conducted by CyberKnife with prescription dose 30-50 Gy in 3-5 fractions. One of the primary endpoints is ADT-free survival of arm B, the other is the time from inception of the study to CRPC. The secondary endpoints include radiotherapy-related toxicity, ADT-related toxicity, bPFS, local PFS and overall survival. Toxicity will be assessed using the National Cancer Institute Common Toxicity Criteria V.5.0.

Ethics and dissemination: This protocol was approved by the institutional review board of Shanghai Changhai Hospital (CHEC2020-101). This is a randomised control clinical trial comparing SBRT to ADT for men with oligometastatic PCa. The study will be performed in compliance with applicable local legislation and in accordance with the ethical principles developed by the World Medical Association in the Declaration of Helsinki 2013. Study results will be disseminated through conferences and peer-reviewed scientific journals.

Trial registration number: Clinicaltrials.gov identifier:NCT04599686.